Preforms are blow molded to produce containers out of a thermoplastic material in a desired shape. The preforms are first thermally conditioned along a transport route in a heating unit. Particularly the preforms are first heated before the subsequent blow molding process is performed. During the blow molding process the preforms are transformed into containers of the desired shape by compressed air.
The distance between the preforms coming out of the heating unit is usually quite small. The preforms are then usually handed over to the subsequently arranged blow molding device by a transfer star or a delivery star. The distance between the preforms has to be enlarged before the blow molding process according to the size and distance of the blow molds.
This is usually done by moving the preform holding clamps in a radial and tangential direction away from each other.
Document WO 2006/050935 discloses a method and a device for the transport of containers that comprise a carrying ring or something alike. Hereby the radial control of the gripping elements is done by a hydraulic or pneumatic device.
DE 10 2006 023 531 A 1 shows a device for the transport of piece goods with a rotary carrier device and a plurality of transport arms, which are swivel mounted on the carrier device. The movement of the at least one carrier arm is independently controlled from the movement of another transport arm.
WO 1998 022374 A1 shows a servo driven, computer controlled transfer system for containers. The system replaces known transfer stars and is able to transport a plurality of containers with different sizes. Because of the servo driven gripping mechanism and the control by a computer this is a so called “intelligent” system. The gripping arms are moved by servo motors, allowing a secure grip of the containers.